The invention relates to a suspension containing sucralfate (sucrose sulfate aluminum salt) as a pharmaceutically effective component.
The sucralfate can combine directly with pepsin in gastric juice to suppress the activity thereof. It has antipepsin and antiacid effects. The sucralfate can form a covering film over mucous membranes of the stomach and duodenum to protect the membrane. This effect is to selectively couple with an ulcer area of the digestive tract for the protection of the diseased part.
Pharmaceutical preparations containing this sucralfate have been provided in the solid form such as tablets, granules, pellets or powders. Since the sucralfate is not water soluble, the liquid form of the preparation must be a suspension but any of the usual assistants cannot hold the suspension stable for a long time.
JP-A 503031/1986 discloses a suspension containing sucralfate, to which 1-5 weight % of xanthan gum and 1-12.5 weight % of at least one peptizer are added. This is not satisfactory, however, in that it is necessary to control the particle dimension of sucralfate to be smaller than 50 .mu.m since if the particle dimension is larger than that the suspension is unstable due to particle sedimentation. Since the amount referred to above of xanthan gum to be added is in relation to sucralfate, the viscosity of the suspension is too low when the sucralfate content therein is fairly small. It is necessary in this case to add glycerin or the like in order to increase the viscosity. In the case where sucralfate is added in a considerable amount in the suspension, this gives a slurry rather than the suspension so as to be difficult to take.
Meanwhile, it is well Known that solid pharmaceutical preparations generally necessitate a considerably long time until the preparations are disintegrated and consequently until the medicinal effect appears, different from liquid pharmaceutical preparations.
In order to prepare an aqueous suspension, it is well known to generally use a dispersing agent such as acacia, carboxy methyl cellulose sodium, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, crystalline cellulose, alginate, gelatin and bentonite.
Since sucralfate produces A .sup.3+ ions in an aqueous medium so as to cause mutual reaction with such dispersing agent, sucralfate particles are bound together to cause rapid sedimentation, whereby the suspension cannot be redispersed or is changed to be in a semi-solid state due to gelation of the dispersing agent under the influence of such ions.
There is a possibility depending on the kind of the dispersing agents that the dispersed phase tends to cause sedimentation gradually from particles of larger dimension and higher density. In the course of a so-called free sedimentation for a long time, agglomeration is formed in the suspension (caking phenomenon) so that even if strongly shaken it is impossible to redisperse. It is necessary for the suspension that not only sedimentation of the dispersed phase is retarded as far as possible but also redispersion can be readily made.